demo-video

Demo Video Assembly Skill

This skill assembles a narrated demo video from ordered visual segments and matching narration audio. It is designed for first-pass walkthrough videos that combine captured prototype frames or clips with per-segment voiceover WAV files.

Overview

The workflow takes a manifest that describes each segment, resolves the visual source, and uses FFmpeg to render each segment into a normalized video clip before assembling the final MP4. It supports hard cuts by default or optional synchronized video and audio fades. The narration track is muxed from WAV files so the output can be reviewed without a separate video-editing tool.

Manifest Schema

Use a segments.yml manifest with optional top-level output settings and an ordered list of segments. Each entry describes a visual source and the narration audio to combine for that portion of the video. All paths resolve relative to the manifest file.

output: ./output/demo.mp4   # optional; destination path for the assembled MP4
resolution: 1280x720        # optional; default 1280x720
fps: 24                     # optional; default 24
transition:                 # optional; omit for hard cuts
  type: crossfade
  duration: 0.5
  fade_in: true
  fade_out: true
segments:
  - type: frame
    visual: ./frames/intro.png
    narration: ./audio/intro.wav
    duration: 4.5
  - type: clip
    clip: ./clips/interaction.mp4
    narration: ./audio/interaction.wav

Top-level fields

• output sets the destination path for the assembled MP4, resolved relative to the manifest; the --output or -OutputPath argument overrides it when supplied
• resolution controls the output width and height in WIDTHxHEIGHT form (default 1280x720); the --resolution or -Resolution argument overrides it
• fps sets the frame rate applied when rendering each segment (default 24); the --fps or -Fps argument overrides it
• transition enables synchronized scene and narration fades; omit it or set it to none to retain hard cuts